The technology for interconnections that are to serve as vias, lines and other patterns and interconnects in integrated circuit and semiconductor chip structures is well developed in the art. In these structures multilevel wiring patterns are embedded in a dielectric material with wiring patterns and vias being separated by dielectric materials with different dielectric properties. Materials such as copper (Cu) are receiving attention in the art as having the potential of being able to improve performance by reducing conductor resistance. However; under the physical conditions of ever smaller dimension and increasing current, driven by the desire for increasing performance, the properties of diffusion and electromigration of such materials, are exhibiting difficult to solve contamination and leakage control problems and reliability issues.
Protective layers, commonly called by such terminology as “liners”, “barriers” or “caps” are being employed in efforts to limit outdiffusion and electromigration. However, any protective materials also have to have good adherence to the various other dielectric materials in the structure.
At the present state of the art; the problems are addressed, in one solution, by using, for copper conductor lines on a silicon substrate using silicon dioxide as the interconnect dielectric material, and the material silicon nitride as the cap material. However the presently relied on silicon nitride material, while having the desired high resistivity properties also has a relatively high dielectric constant of 7 to 8 which operates to increase the effective dielectric constant of the structure (Keff) and may also detrimentally affect the intralevel capacitance.
In another solution; also directed to the diffusion and electromigration problems for the material Cu, the desired results are achieved including the further ability to be able to select a capping material that maintains the desired low (Keff) established by the surrounding dielectric material. That technology is described in application Ser. No. 09/361,573 filed Jul. 27, 1999, of Hu et al, and is assigned to the assignee of this application. In that technology a self aligned metal cap is produced in a two step procedure involving Cobalt Tungsten Phosporous (CoWP) deposition. The deposited material covers and protects the top copper surface while achieving the desired adhesion in the structure and to serve as an impedance to electromigration.
As further progress in the art is sought, low dieletric constant (low k) intermetal dilectric materials appear to have the more promising properties
A need is present for a simpler procedural approach in integrated circuit technology wherein a conductor material such as Cu is protected from the effects of electromigration and diffusion yet can be positioned in a selectably low Keff dielectric structure.